This invention relates to a computer system including a storage subsystem, a host computer, and a management computer. In particular, this invention relates to a technique of relocating data stored in a storage subsystem.
Recent storage subsystems often take the form of a RAID disk array system where plural disks are integrated. With a RAID configuration, storage subsystems are improved in reliability and performance.
A RAID disk set is called an array group. Array groups virtually constitute logical volumes, and host servers access storage subsystems on a logical volume basis. When too many host servers access the same array group at the same time, the performance of all logical volumes belonging to the array group is lowered. To cope with this problem, several techniques have been proposed to avoid a flood of access to one array group.
One known example of such techniques is disclosed in JP 2003-140836 A. This technique is to set a performance limit to an array group and move data from the array group to another when the limit is exceeded. In this way, the array group can meet a performance level requested by a user.
Another known example is disclosed in JP 2005-050007 A. This technique is to relocate data in a manner that enables a storage subsystem to fully exert its performance potential. According to this technique, service levels are set to various resources of a storage subsystem, and data is relocated so that the set service levels are met. Various resources refer to a ratio of how much of a disk is consumed, a disk capacity, and the like.